1. Field of Invention
The present invention relates to fabric made portable seat products, and more particularly to a seat support arrangement for folding chair which can evenly distribute a downward pulling force on the fabric seat and minimize a stress around the supporting ring.
2. Description of Related Arts
Referring to FIG. 1 of the drawing, a conventional portable chair comprises a foldable chair frame constructed by metal tubes and a chair seat made of durable fabric wherein the foldable chair frame A1 is constructed by a pair of back legs A11 to provide a back frame A2 and a seat frame A3 for supporting a fabric seat B1. The back frame A2 and the seat frame A3 are arranged in such a manner that the chair frame A1 can be easily opened to provide a rigid cross-support for use and be folded up for storage.
The conventional method of attaching the fabric seat B1 to the chair frame A1 is to affix an upper end B2 of the fabric seat B1 to a top end of the back frame section A2 and to have two leg placement holes B11 reinforced by two lining pads B12 at two front comers of the fabric seat B1 for mounting a front end B3 of the fabric seat B1 on the seat frame A3. The conventional fabric seat B1 is attached to the seat frame A3 by slipping the placement holes B11 over the frame extension legs of the seat frame portion of the chair. The seat can then be hooked over the top of the back frame A2 to secure the back of the fabric seat B1 to the frame. This means that at least two leg placement holes B11 on the front portion of the fabric seat B1 are needed for attaching the conventional fabric seat B1 to the front portion of the seat frame A3.
All typical frame legs, including two front frame legs A11a, are cylindrical hollow leg and the two leg placement holes B11 of the conventional fabric seat B1 are circular holes reinforced with two lining pads B12 which are affixed on top of two front frame joints A12 by means of a pair of affixing plugs B13.
However, these conventional structures of mounting the front end B3 of the fabric seat B1 to the frame joints A12 of the chair frame A1 have inherent problems when the chair is used. Since the two front frame legs A11a are supported inclinedly and pivotally in cross manner but not in vertical manner, an individual sitting down on the fabric seat B1 causes stress to the lining pads B12 of the leg placement holes B11 of the fabric seat B1. This causes the leg placement hole B11 to be stretched and misshapen, or worse, torn open, as a pulling pressure is applied to the lining of the leg placement holes B11 as in individual sits on the fabric seat B1.
When an individual sits down, an angle is created on the fabric seat B1 from the downward pulling force on the fabric seat B1 at the point where the edge of the support ring is pulled from a stress created at the edge of the support ring ends. An individual's weight causes the fabric seat B1 to be pulled away from the edges of the two placement holes B11. Therefore, the fabric seat B1 at the edges of the leg placement holes B11 are pulled from a stress created at the edges of the leg placement holes B11. At the same time, each of the lining pads B12 itself causes an opposite downward pulling force on the fabric seat B1 at the same stress point. As a result, the fabric seat B1 will be distorted at the edge of the leg placement hole B1, creating a pointed ridge at the edge of the leg placement hole B11.
In other words, the stress on the fabric seat B1 has simply been transferred from the lining pads B12 of the leg placement holes B11 to a point just off each of the leg placement holes B11. The stress created will then cause a tear, not at the leg placement hole B11, but along the edge of the leg placement hole B11. Also, the fabric will be permanently misshapen at the stress point over a period of continued use.
Besides, in order to reduce the folding size of the of the chair frame A1 of the folding chair for easy storage and carrying, the two front frame legs A11a are made as closed to the back legs A11 as possible. However, the sitting area of the fabric seat B1 which substantially supports the weight of the user is limited too. Normally, such a limited sitting area of the fabric seat can merely support the buttock portion and an upper portion of the thigh of the user. Therefore, most of the users of the conventional folding chair have an intention to slide out of the seat frontwardly.